Antioxidant



presence of an acid catalyst.

pa e

ANTKOYUD'ANT Arthur W. Sloan, Stow, Ohio, assignor to The- B. F. Goodrich Company,

New York, N. Y., a

corporation of New York No Drawing. Application September 25, 1941, Seriai No. 412,304

20 Claims. 260-809) This invention f relates to the preservation of rubber and of articles made from rubber, and also to the preservation of other oxidizable organic compounds. It pertains specifically to the antioxidant properties of the products obtained by reacting diarylamines with conjugated diolefins in thepresence of an acidic catalyst.

It has already been proposed to employ the reaction products of certaingunsaturated hydro-' carbons with diarylamines as. antioxidants for organic materials which tend to decompose by absorption of oxygen from the atmosphere. In particular, it has been proposed to' react the terpenes with diarylamines in the presence of an acidic catalyst, and to use the products of the-reaction as antioxidants for rubber.- Rubber compositions containing small amounts of these age-resisters show a resistance to deterioration by aging in air or oxygen which is superior to that of a similar rubber composition containing no antioxidant. The terpene hydrocarbons may have one or more carbon-carbonv double bonds. In general, however, these dou- 'ble bonds arenot conjugated. Similar results may be obtained with other similar .olefins.

I have now discovered that antioxidants greatly superior to the afore-mentioned materials may be obtained by reacting open-chain conjugated diolefins containing less than eight carbon atoms in the chain with diarylamines in the Among the hydrccarbons' which give satisfactory results are butadiene-Lfi; piperylene (pentadiene-LB); isoprene; 2-methyl pentadiene-1,3; 2,3dimethyl butadiene 1,3; 2,3 dimethyl pentadiene 1,8; hexadiene-.1.3; Z-methyl hexadiene-l,3;- S-methyl hexadiene-ifi; hexadiene-za; heptadiene-2,4; heptadlene-EB; and other similar compounds. Among the diarylamines which yield suitable products are diphenylamine, phenyl-alphanaphthylamine, phenyl-beta-naphthylamine, the

ditolylamines, the phenyltolylamines, the dinaphthylamines, aniline tetraphenylmethane, bhenyl-p-xenylamine dixenylamine, dianilinm diphenylmethane, p-hydroxydiphenylamine, paminodiphenyiamine, U, N'-diphenyl-p-phenylenediamine, anilino-bi-phenylene oxide, anilinoacridine, 6-anilino ouinoline, p-chlorodiphenylamine, p-isopropoxydiphenylamine, and the like. Reaction products of diarylamines with alcohols, aldehydes, and ketones are also the chemical equivalents of the diarylamines themselves for this reaction.

The catalysts which may be used for the syn thesis of my new antioxidants comprise such materials as HCI, rnPo;, H=soi, NaHSOM, anon, A1013, BFs, SnCh, NH4B1, I2, etc. In general,

any of the well-known acidic condensation catathe'reaction is carried out as hereinafter'described.

The reaction can usually-be carried out at a temperature of 50 to 300 0., and at either atmospherlc or elevated pressure, depending upon the reagents used.

As a specific example of my invention I have prepared an antioxidant by heating one molecular equivalent of butadiene with two molecular equivalents of diphenylamine in the presence of 0.1 molecular equivalent of zinc chloride at a temperature of about 200 C. for four to five hours in an autoclave equipped with a stirrer. The reaction mixture is then washed with hot water under pressure and with a strong caustic solution. The mixture, after heating at reduced pressure to distill off the unreacted hydrocarbon and diphenylamine, is a dark oily liquid.v

The relative proportions of the reactants are not restricted to those of the specific example, but may be varied over a wide range. In general, neither reactant should be present in an amount greatly exceeding six times that of the other. The relative proportions used in. the ex ample, however, give better resultsthan other mixtures.

The product consists largely of a diarylamine containing a nuclear-substituted unsaturated hydrocarbon side-chain, but other, compounds hitherto unknown, among which are some allcyclic compounds, are also present. It is impossible to obtain the reaction products of this invention, with their superior antioxidant properties, by any other known means.

As an example of the antioxidant power of these compounds, I have prepared the following rubber composition in which the part are by Weight:

Rubber 100.0

Antioxidant pear to be mutual activators.

see

The following table gives the ultimate tensile strength (T) in pounds per square inch, and

ultimate elongation (E) in per cent for the foregoing composition containing various antioxidants cured at 279 F. for 30, 60, or 90 minutes,

and aged as indicated. Sample A contained no antioxidant; sample B contained the butadienediphenylamine reaction product described above as a typical example of my new antioxidant; sample C contained a product made by condens ing two molecular proportions of diphenylamine with one molecular proportion of pentene-Z under the same conditions, as a typical example of unconjugated olefin-diphenylamine reaction products.

Before agin Cure, time in minutes E T E T Aged 96 hours in Bierer-Davis Bomb (In oxygen at 70 0. and 300 lb./sq. in.)

A B O Cure, time in minutes in -example C was compounded in the same rubber composition as was'used in the foregoing examples. The ultimate tensile strength and elongation of the composition were measured before and after aging 96 hours in oxygen at a pressure of 300 lb. per sq. inch and 70 0..

Before agin ems r aging Cure The compositions were also aged 14 days in a Geer oven at 70 C. and flexed on a DeMattia flexing machine at 80 F. at the rate of 300 flexures per minute. On a scale ranging from (no cracks) to (rupture), B was rated 4.2, C 6.2, while the sample containing the mixture was V only 2.5 after 1,100,000 flexures- Similar results can be obtained by using mixtures of other alkylated diaryl amines and the reaction products of conjugated diolefins of any chain length with diarylamines. The alkylated dia yl s m y be prepared by reacting olefins, such as butene- 2, pentene-Z, hexene-l, hexene-2, a heptene, an

octene, etc., with a diarylamin'e in the presence of an acidic catalyst under conditions similar to those used for the conjugated diolefin reaction.- Or, if desired, an alcohol may be condensed with a diarylamineunder similar conditions. Suitable alcohols comprise the butanols,

the pentanols, diisopropyl carbinol, the hexanols, the heptanols, and the like.

My new compounds are eflective in amounts ranging from 0.1 to 5% of the rubber composition. The may also be used for the pre'servation of other organic substances which tend to deteriorate in the presence of oxygen, such as fish oils,'linseed oil, tung oil, gasolines containing unsaturates, and-the like. They are effective with any kind of rubber, such as caoutchouc, balata, gutta percha, latex, reclaimed rubber, artificial rubber isomers, and such synthetic rubbers as polychloroprene, copolymers of butadiene with acrylonitrile, styrene, methylacrylate, methyl methacrylate, isobutylene, and other copolymerizable monomers.

These new antioxidants may be added to the. I

material to be, preserved in any suitable manner. They may be added in the form of a solution, or dissolved as they are. They may be added to rubber, for example, on a roll mill or in an internal mixer or by any other suitable method. They may be applied to the surface of the rubber composition either in their pure fori'n or as a inner tubes, latex dipped goods, etc.

solution in a suitable solvent, or they maybe dispersed in the rubber latex. They are applicable to any type or rubber or synthetic rubber composition such as, those used in the manufacture of hose, belting, rubber threads, rubberized fabrics, boots, shoes, molded goods, tires and They may be used in conjunction the ordinary pigments, fillers, dyes, accelerators of vulcanization or other antioxidants used in rubber compositions; V

Although I have herein myself thereto, for many modifications and var-' iationlz will be apparent to those skilled in the art. I c i. The method of retar the deterioration of materials which tend todecompose in e ence of oxygen which comprises treating them with the product obtained by cond t .it: a coniugated diolefln cong less than eight carbon atoms with a diarylamine in the presence of an acidic condensation catalyst.

2. The method of prese comprises treating it with a :-:-i .1 1. comprising a substantial proportion of each of two ingredients, an alkylated diaryl tartand the product obtained by condensing a conjugated dioiefin with a diarylamine in the presence or an acidic condensation catalyst. I

3. The method of retarding the deterioration of materials which tend to decompose in-the,presence of oxygen which comprises treating them with the product obtained by condensing a'conjugated diolefin containing less than eight .car-

bon atoms with diphenylamine in the presence of,

an acidic condensation catalyst.

4. The method of preserving a rubber which,

with any of k V disclosed specific examples of my invention, I do not intend to limit I a rubber which aa'zaoao comprises treating it with the product obtained by condensing a conjugated dioleiin containing less than eight carbon atoms with a diaryiamine in the presence of an acidic condensation cata lyst.

5. The method of preserving a rubber which comprises treating it with a mixture comprising a substantial proportion of each of two ingredients, an alkylated diarylamine and the product obtained by condensing butadienc-i.,3 with a diarylamine in the presence of an acidic condensation catalyst.

6. The method of preserving a. rubber which comprises treating it with the product obtained by condensing a conjugated diolefin containing less than eight carbon atoms with diphenylamine in the presence of an acidic condensation catalyst.

7. The method of preserving a rubber which comprises treating it with the product obtained by condensing butadiene-Lii with a diaryiamine in the presence of an acidic condensation cataiyst.

8. The method of preserving a rubber which comprises treating it with the product obtained by condensing butadienelfi with diphenyiamine in the presence of an acidic condensation catalyst.

9. The method of preserving a rubber which comprises treating it with the product obtained by condensing isopi'ene with a diaryla'mine in the presence of an acidic condensation catalyst.

10. The method of preserving a rubber which comprises treating it with a mixture comprising a substantial proportion of each of two ingredients, an alkylated diarylamine and the product obtained by condensing butadiene-i,3 with diphenylamine in the presence of an acidic condensation catalyst. v

11. The method of preserving a rubber which comprises treating it with the product obtained by condensing piperylene with a diarylamine in the presence of an acidic condensation catalyst.

12. A rubber composition comprising a rubber and a mixture comprising a substantial proportion or each of two ingredients, an alkylated diarylamine and the product obtained by con-- densing a. conjugated diolefln with a diarylamine in the presence of an acidic condensation cata-' lyst.

a 13. A rubber composition comprising a rubber and the product obtained by condensing a conjugated diolefin containing less than eight carbon atoms and a diarylamine in the presence of an acidic condensation catalyst.

ii. A rubber composition comprising a rubber and the product obtained by condensing a conjugated diolefin containing less than eight carbon atoms with diphenylamine in the presence of an acidic condensation catalyst.

15. A rubber composition comprising a rubber and the product obtained by condensing buta dime-1,3 with a diarylamine inthe presence of an acidic condensation catalyst.

16. A rubber composition comprising a rubber and the product obtained by condensing butadiene-1,3 with diphenylamine in the presence of an acidic condensation catalyst.

17. A rubber composition comprising a rubber and the product obtained by condensing isoprene with a diarylamine in thepresence of an :acidic condensation catalyst.

18. A rubber composition comprising arubber and a mixture comprising a'substantial proportion of each of two ingredients, an alkylated diarylamine and the product obtained by condensing butadiene-1,3 with a diarylamine in the presence of an acidic condensation catalyst.

19. A rubber composition comprising a rubber and the product obtained by condensing piperylens with a diarylamine in the presence of an acidic condensation catalyst.

20. A rubber composition comprising a rubber and a mixture comprising a substantial proportion of each of two ingredients, an alkyiated diarylamine and the product obtained by condensing butadiene-1,3 with a diarylamine in the presence of an acidic condensation catalyst.

ARTHUR w. SIDAN.

CERTIFICATE OF CORRECTION. Patent No. 2,579,956. July 10, 1915.

ARTHUR w. SLOAN.

of the above numbered patent requiring correction as follows: Page 1, first column, line #6, for "U5" read --N,--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. v

Signed and sealed this 11th day of December, A. D. 1915.

Leslie Frazer (s l) First Assistant Commissioner of Patents. 

